Tube system for heat exchange



Dec. 15, 1936. P. DMITREVSKIJ ET AL 2,064,246.

TUBE SYSTEM FOR HEAT EXCHANGE I Filed April '7, 1954 9 q I xgln I I liKXQ I II I l x Patented Dec. 15, 1936 UNITED STATES PATENT OFFICE PetrDmitrevskij and Dimitrij Astrov, Prague, Czechoslovakia ApplicationApril '7,

1934, Serial No. 719,522

In Czechoslovakia April 11, 1933 3 Claims.

The subject of the invention relates to improvements in and relating totube systems for heat exchange of a type wherein e. g. the heated liquidmedium inside the tubes is subjected to an uninterrupted forcedcirculation, for instance by means of a pump, while the gaseous mediumused for heating, flows round the tubes.

According to the invention the eifective area of the tube is an annularchannel formed by introducing into the tube for its whole length a core,which compels the liquid to flow merely through the annular channel. Ahelically shaped body is furthermore introduced into the said annularchannel so that the water flowing through the tube under pressure isthrown by centrifugal force against the inner surface of the tube andreceives a helicoidal movement round its longitudinal axis. If theflowing liquid surpasses a certain angular velocity it is separated bycentrifugal force from steam and since specific weight of the liquid isgreater than that of its steam it will form a continuous layer on theperiphery of the pipe and the steam will collect at the inner surface ofthe annular channel.

In the tube system, according to the invention the speed of the liquidforced through the helical passage is such that when using a heatingintensity of about 20,000 calories per square foot of heating surfacethe liquid should make about 25 to 30 turns per second round the axis ofthe tube. The corresponding axial speed of the liquid through the tubedepends upon the pitch of the helical guide surface.

The invention refers, further, to means for automatic control of theamount of liquid flowing through the annular channel in relation to therate of heating; the result aimed at is obtained by fixing the core ofthe tube only at one end, whereas its other extremity is relativelymovable. If the heating of the tube be increased, the latter will besubjected to thermal dilatation more than the core, wbich'causes anincrease of the intake annular cross section between core and tube atthe free extremity of the core.

On the accompanying drawing, several modes) of carrying the inventioninto practice are given, by way of example. Fig. 1 is an axial elevationof a heat exchange tube according to the invention, Fig. 2 shows anelevation of a simplified arrangement, Fig. 3 is a lateral section of atube with a core of the same design, on the line 33 of Fig. 2; Fig. 4 isa schematic general view of a system of water tubes for a steam boiler(front View); Fig. 5 is the corresponding schematic'al side view, andFig. 6 is a similar side view of the system with double tubes.

According to the example shown in Fig. l, a cylindric core 2 preferablybeing in itself a tube is located in the outer tube I. The tube Iextends on both its extremities to the headers 3 and 4, into which it isexpanded. The tubular core 2 is closed at its right end by means of plug5, which is attached to an inner cover 6, placed inside the header 3,which itself is closed from outside by the outer cover 8. The plug 5,the outer and inner covers 6 and 8 are connected together and tightenedto the header 3 by a screw I and an outer nut. In this manner thetubular core 2 is rigidly and unmov- II) having a conical inner surfaceI0 adjacent:

the conical end of the core 2.

The header i is provided with an intake pipe I3 and a removable coverI6; the header 3 has, similarly, an outlet pipe I l and a removablecover I5. for the headers 3 and 4, respectively, for the purpose ofpermitting access to the interior of said headers and the pipes attachedthereto.

In the annular channel between the inn r surface of the pipe I and theouter surface of the core 2 a helicoidal guiding surface 22 is placedwhich is fixed e. g. to the surface of the core 2. The liquid medium, e.g. water, forced through the tube by pressure generated These covers I5and It are provided" by a suitable pump must flow through the annu larchannel between the inner surface of pipe I and the core 2 along thehelical course 22, thus being subjected to a rotary motion; the liquidis thereby subjected to centrifugal force which throws it from the axisof the tube I to the inner surface thereof and owing to its higherdensity, separates the water from the steam which is formed by the heatreceived from the outer tube I. The steam flows in a helical path alongthe surface of the inner core 2. The greater the temperature of theheating medium which heats the outer surface .of the pipe I, the greatershould be the amount of the heated medium, flowing through the annularchannel between the tube I and the core 2. This amount is automaticallyregulated by, varying the space between the ring ID in the free end ofthe tube I inside the chamber of the header 4 and the conical extension9 on the free end of the core 2, which latter, not being heated directlyis subjected to smaller dilatation than the tube I.

Hence, with increased heating of the pipe, the intake space between thebodies 9 and III for the heated medium is increased also, since the ringI9 slides away from the conical extremity 9 of the core 2, which expandsless than the tube. If the heating of the tube I is smaller it expandsless and therefore the cross-section for the flowing liquid iscorrespondingly less.

The length of the core 2 with its conical extension 8 and the rod 23varies also with the intensity of heating. Under such conditions the rod23 slides in the bore 24 and the size of the cylindrical space 24between the free end of the rod 23 and the bottom of the cover II variescorrespondingly, which may be utilized in the following three ways:

1. For the control of efficiency either of the whole tube system or ofits individual parts,

2. For the automatic variation of the amount of the medium whichcirculates through the system,

3. For automatic regulation of the amount of heat which serves to heatthe whole system of tubes.

It is sufiicient for this purpose to fill the hollow space 24 with aliquid and connect this space by means of a pipe I! to a pressurecylinder of a suitable design which serves either to record a graph ofpressure variations or to control a suitable gear for introducing theheating medium into the system or to control the development of theheat.

Figure 2 shows a modified form of an embodiment of this invention,similar to the form shown in Figure 1, except that the spiral rib 22 isomitted. In certain cases it has been found sufiicient to providecontrol of the water flow through the tube by means of the automaticvalve arrangement shown in Figure 1.

The Figs. 4 and 5 represent schematically. an arrangement of a pluralityof heat exchange tubes such as are shown in Figs. 1 or 2 with the intakeand outlet tubes I3 and I4, with the steam-chest I8 the circulating pumpl9 and the corresponding connecting piping 25.

In the arrangement shown in Fig. 6, two series of tubes I and 2| areemployed provided with a double chamber 20, common to both series oftubes. One series thereof, e. g. the system 2I having no cores or nohelical surface according to Fig. 2,

In the tube systems serving for cooling :1- given medium or forsuperheating of steam, the tubes I are pressed in on both its ends notto the headers, but to the plates, and the cores are fixed at one end toa parallel plate, which is fixed at certain points to the plate intowhich the tubes are adjusted, and which replaces the cover 6 and theheaders 3 according to Fig. 1. On the other end, where the extremitiesof the tubes I may freely move with respect to the ends of the cores 2,the covers I I of the headers 4 are replaced again by a plate, which isconnected by means of screws to another plate to which the ends of thetubes I are pressed in.

The hollow spaces 24 are here replaced by small cylinders, one for everyindividual core, the said cylinders being connected to the plate, whichreplace the covers II.

The whole arrangement may be employed in tubular systems of any designserving to evaporate, heat, cool or condense any kind of steam orvapours, and to use any required heating or heated media.

The core 2 may be replaced, in certain cases by guiding spiral surfaces,which serve to change the direction of the flowing medium towards theinner surface of the tube I. Also the number of helices located on thecore may be chosen freely and the angle of the helical curves need notremain invariable along the whole core; this angle may preferably beincreased particularly at both ends of the tubes. Instead of using achoking ring II] it is also possible to reduce the diameter of the endof pipe I adjacent to this ring, or to provide this end of said pipewith a conical extension, similar to ring I0.

What we claim is:-

1. In a tube system for liquid evaporators, a plurality of tubes, meansfor passing a fluid medium through said tubes, a core member positionedcentrally in each of said tubes, means for fixing one end of each ofsaid core members with respect to its tube, means positioned on each ofsaid core members for dividing the space between the core and tube intoa helical path and means positioned at the free end of each of said coremembers for controlling the flow of said fluid medium through its tubein accordance with the difference of expansion of the tube and core.

2. In a tube system for liquid evaporators, a plurality of tubes,adapted to be externally heated, means for passing a liquid through saidtubes, means for dividing the passage through each of said tubes into acontinuous helical path for imparting a high velocity, rotary motion tosaid liquid sufficient to separate said liquid from the vapor formedtherein and suffici'ent to force said liquid outward into intimatecontact with the hot inner surfaces of each of said tubes as said liquidis passed through said tubes.

3. A tube system for liquid evaporators, comprising a plurality ofelongated tubes, headers connected to the ends of said tubes, said tubesbeing adapted for heating on the outside, core members positioned insideof said tubes, one end of each of said core members being attached toone of said headers, helical members positioned on said core members fordividing the space between each of said core members and the innersurface of its tube into a continuous helical path, the angle of saidhelical path with respect to said core member being sufficient to imparta rotary motion to the liquid flowing through said tube to separatevapor from said liquid and to force the liquid against the hot innersurfaces of said tubes.

PETR DMITREVSKIJ. DIMI'I'RIJ ASTROV.

